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Abstract:

A method for performing a random access procedure by a User Equipment
(UE) in a mobile communication system includes transmitting a preamble
for identifying the UE, through a first message; receiving a second
message from an Evolved Node B (ENB) in response to the first message,
the second message including uplink (UL) transmission resource
information for transmitting at least one of a transparent Radio Resource
Control (RRC) message which is an RRC message that a UE having no RRC
control connection transmits for the first time, and Buffer Status Report
(BSR) information indicating an amount of UL data; setting a format
indicator indicating if the transparent RRC message or the BSR
information is included in a third message; and generating the third
message according to the set format indicator, and transmitting the
generated third message according to the UL transmission resource
information.

Claims:

1. A method for performing a random access by a User Equipment (UE) in a
mobile communication system, the method comprising: transmitting a
preamble to identify the UE via a first message; receiving a second
message from an Evolved Node B (ENB) in response to the first message,
the second message including uplink (UL) transmission resource
information for transmitting at least one of a transparent Radio Resource
Control (RRC) message, which is an RRC message that a UE having no RRC
control connection transmits for the first time, and Buffer Status Report
(BSR) information indicating an amount of UL data; setting a format
indicator indicating if the transparent RRC message or the BSR
information is included in a third message; and generating the third
message according to the format indicator and transmitting the generated
third message according to the UL transmission resource information.

2. The method of claim 1, wherein if the transparent RRC message is
included in the third message, the format indicator includes a first bit
of a first Medium Access Control (MAC) subheader of the third message,
and the transparent RRC message is provided after the format indicator.

3. The method of claim 1, wherein if the transparent RRC message is
included in the third message, the format indicator includes first two
bits of a first MAC subheader of the third message, and the transparent
RRC message is provided after the format indicator.

4. The method of claim 1, wherein if the BSR information is included in
the third message, a first bit of a first MAC subheader of a MAC Packet
Data Unit (PDU) transmitted via the third message is set as the format
indicator indicating that the transparent RRC message is not included in
the third message, and the BSR information is provided after the format
indicator.

5. The method of claim 1, wherein if the BSR information is included in
the third message, first two bits of a first MAC subheader of a MAC PDU
transmitted through the third message are set as the format indicator
indicating that the transparent RRC message is not included in the third
message, and the BSR information is provided after the format indicator.

6. A User Equipment (UE) apparatus for performing a random access in a
mobile communication system, comprising: a physical layer processor for
exchanging messages with an Evolved Node B (ENB); a Medium Access Control
(MAC) controller for controlling to transmit a preamble to the ENB via a
first message, acquiring uplink (UL) transmission resource information
from the ENB in response to the first message via a second message that
the physical layer processor received from the ENB, the UL transmission
resource information being used for transmitting at least one of a
transparent Radio Resource Control (RRC) message indicating that a UE
having no RRC control connection transmits for the first time, and Buffer
Status Report (BSR) information indicating an amount of UL data,
generating a MAC control message containing therein the BSR information,
and outputting a format indicator indicating whether the transparent RRC
message or the BSR information is included in a third message which is
transmitted using the UL transmission resource information; and a MAC
multiplexer for multiplexing a MAC control message including at least one
of the transparent RRC message delivered from an upper layer and the BSR
information delivered from the MAC controller, and generating the third
message according to a format indicator designated by MAC controller.

7. The UE apparatus of claim 6, wherein if the transparent RRC message is
included in the third message, the format indicator includes a first bit
of a first MAC subheader of the third message, and the transparent RRC
message is provided after the format indicator.

8. The UE apparatus of claim 6, wherein if the transparent RRC message is
included in the third message, the format indicator includes first two
bits of a first MAC subheader of the third message, and the transparent
RRC message is provided after the format indicator.

9. The UE apparatus of claim 6, wherein if the BSR information is
included in the third message, a first bit of a first MAC subheader of a
MAC Packet Data Unit (PDU) transmitted through the third message is set
as the format indicator indicating that the transparent RRC message is
not included in the third message, and the BSR information is provided
after the format indicator.

10. The UE apparatus of claim 6, wherein if the BSR information is
included in the third message, first two bits of a first MAC subheader of
a MAC PDU transmitted through the third message are set as the format
indicator indicating that the transparent RRC message is not included in
the third message, and the BSR information is provided after the format
indicator.

11. A method for performing a random access by an Evolved Node B (ENB) in
a mobile communication system, the method comprising: receiving a
preamble for identifying a User Equipment (UE), from the UE via a first
message; transmitting uplink (UL) transmission resource information via a
second message in response to the first message, the UL transmission
resource information being used for transmitting at least one of a
transparent Radio Resource Control (RRC) message indicating that a UE
having no control connection transmits for the first time and a Buffer
Status Report (BSR) indicating an amount of UL data; receiving a third
message transmitted through the UL transmission resource information;
checking a format indicator indicating if the third message includes the
transparent RRC message or the BSR; and processing the third message in
an RRC layer or a Medium Access Control (MAC) layer according to a set
value of the format indicator.

12. The method of claim 11, wherein processing comprises: if the format
indicator indicates that the transparent RRC message is included in the
third message, processing the third message in the RRC layer.

13. The method of claim 11, wherein processing comprises: if the format
indicator indicates that the BSR information is included in the third
message, processing the third message in the MAC layer.

14. The method of claim 11, wherein if the transparent RRC message is
included in the third message, the format indicator includes a first bit
of a first MAC subheader of the third message, and the transparent RRC
message is provided after the format indicator.

15. The method of claim 11, wherein if the BSR information is included in
the third message, a first bit of a first MAC subheader of a MAC Packet
Data Unit (PDU) transmitted through the third message is set as the
format indicator indicating that the transparent RRC message is not
included in the third message, and the BSR information is provided after
the format indicator.

16. An Evolved Node B (ENB) apparatus for performing a random access in a
mobile communication system, comprising: a Medium Access Control (MAC)
controller for receiving a preamble for identifying a User Equipment (UE)
from the UE via a first message to perform the random access procedure,
transmitting a second message including therein uplink (UL) transmission
resource information to the UE corresponding to the preamble, and
processing Buffer Status Report (BSR) information included in a third
message received from the UE; a physical layer processor for exchanging
the first message, the second message and the third message with the UE;
and a MAC demultiplexer for checking a format indicator of the third
message received from the physical layer processor to determine if the
transparent Radio Resource Control (RRC) message is included in the third
message or the BSR information is included in the third message,
delivering the BSR information to the MAC controller if the BSR
information is included in the third message, and delivering the
transparent RRC message to a Layer 2 (L2) processor if the transparent
RRC message is included in the third message, wherein the transparent RRC
message indicates that a UE having no RRC control connection to the ENB
transmits for the first time, and the BSR information indicates an amount
of UL data.

17. The ENB apparatus of claim 16, wherein if the transparent RRC message
is included in the third message, the format indicator includes a first
bit of a first MAC subheader of the third message, and the transparent
RRC message is provided after the format indicator.

18. The ENB apparatus of claim 16, wherein if the BSR information is
included in the third message, a first bit of a first MAC subheader of a
MAC Packet Data Unit (PDU) transmitted via the third message is set as
the format indicator indicating that the transparent RRC message is not
included in the third message, and the BSR information

Description:

CROSS RELATED APPLICATION AND CLAIM OF PRIORITY

[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/187,735, which claims the benefit of the earlier
filing date, under 35 U.S.C. §119(a), to those patent applications
filed in the Korean Intellectual Property Office on Aug. 7, 2007 and
assigned Serial No. 2007-79270, on Nov. 6, 2007 and assigned Serial No.
2007-112879, on Jan. 4, 2008 and assigned Serial No. 2008-1244, and on
Feb. 5, 2008 and assigned Serial No. 2008-12001, the disclosures of all
of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to mobile communication systems and
more particularly to a method and apparatus for performing a random
access procedure in a mobile communication system.

[0004] 2. Description of the Related Art

[0005] In Long Term Evolution (LTE) whose standardization work is being
conducted in 3rd Generation Partnership Project (3GPP) as one of the
next generation mobile communication systems, an Evolved Node B (ENB)
takes charge of scheduling downlink (DL) and uplink (UL) traffics. In the
communication system where the ENB takes charge of the scheduling, a
procedure for transmitting UL data includes the following five steps.

[0011] With reference to FIG. 1A, a description will now be made of a
process in which a UE makes a buffer status report by sending a
scheduling request message to an ENB in an LTE system.

[0012] The message that the UE sends in Step 1 is referred to as a
scheduling request message, the resources over which the scheduling
request message are called scheduling request transmission resources (or
scheduling request resources), and the periodically repeated scheduling
request resources can be allocated to a UE in the state where its Radio
Resource Control (RRC) connection is set up. For example, particular
transmission resources can be given to a particular UE as scheduling
request transmission resources every 10 msec. When there is a need for
data transmission over UL, a UE 105 that has the periodically-existing
scheduling request transmission resources sends a scheduling request
message to an ENB 110 through the scheduling request resources in step
115.

[0013] The scheduling request message can be expressed with a single bit
of (1-bit) information, and the UE 105 requests transmission resource
allocation for buffer status report using the 1-bit information. In step
120, the ENB 110 sends a UL grant message to allocate to the UE 105 as
many transmission resources as the UE 105 may send in a BSR message for a
buffer status report. In step 125, the UE 105 sends the BSR message
containing the type and size of the generated data to the ENB 110 through
the transmission resources allocated in step 120 through the UL grant
message.

[0014] Based on the BSR message, the ENB 110 estimates priority of the
data, and allocates transmission resources to the UE 105 at an
appropriate time so that it can transmit UL data, taking into account
both the channel state of the UE 105 and the traffic condition of the
current cell.

[0015] FIG. 1B is a diagram illustrating an example of a BSR message used
in an LTE system.

[0016] The BSR message, since it is a Medium Access Control (MAC) control
message made by a MAC layer, is a kind of a MAC control Service Data Unit
(SDU), and is contained in a normal MAC Packet Data Unit (PDU) 140 before
being transmitted. The MAC PDU 140 is generated with a MAC header 130 and
a MAC SDU 135, The MAC header 130 contains the type and size of the MAC
SDU 135. The terms `PDU` and `SDU` refer to the data that underwent a
particular operation in an arbitrary protocol device, and when the data
generated in an upper layer is delivered to an arbitrary protocol device,
the upper layer data is called `SDU`. Similarly, when the protocol device
generates its own control information, the control information is also
called `SDU`. However, the SDU, to which a predetermined protocol header
is added, is called `PDU`.

[0017] Since the ENB cannot allocate scheduling request resources to all
UEs to which it has RRC connections, the ENB allocates no scheduling
request resource to the UEs having a lower frequency of data
transmissions. Since the only UL channel that the UE can use, which is
not allocated scheduling request resource evens though its RRC connection
has been set up, is a random access channel, the UE which is not
allocated scheduling request resource sends a BSR message to the ENB
through a random access procedure. However, no definition has been given
of a method in which the UE in the state where its RRC connection is set
up sends a BSR message to the ENB through the random access procedure.

SUMMARY OF THE INVENTION

[0018] An aspect of the present invention is to provide a method and
apparatus by which a UE, which is allocated no scheduling request
resource even though its RRC connection has been set up, sends a Buffer
Status Report (BSR) message to an ENB through a random access procedure,
and the ENB receives the BSR message.

[0019] Another aspect of the present invention is to provide a method and
apparatus by which a UE, which is allocated no scheduling request
resource even though its RRC connection has been set up, sends a BSR
message to an ENB through a random access procedure, and the ENB receives
the BSR message from the UE.

[0020] Another aspect of the present invention is to provide a method and
apparatus for transmitting and receiving messages used for performing a
random access procedure between a UE and an ENB.

[0021] According to one aspect of the present invention, there is provided
a method for performing a random access procedure by a User Equipment
(UE) in a mobile communication system. The method includes transmitting a
preamble for identifying the UE, through a first message, receiving a
second message from an Evolved Node B (ENB) in response to the first
message, the second message including uplink (UL) transmission resource
information for transmitting at least one of a transparent Radio Resource
Control (RRC) message which is an RRC message that a UE having no RRC
control connection transmits for the first time, and Buffer Status Report
(BSR) information indicating an amount of UL data, setting a format
indicator indicating if the transparent RRC message or the BSR
information is included in a third message, generating the third message
according to the set format indicator, and transmitting the generated
third message according to the UL transmission resource information.

[0022] According to another aspect of the present invention, there is
provided a method for performing a random access procedure by a User
Equipment (UE) in a mobile communication system. The method includes
transmitting a preamble to an Evolved Node B (ENB) through a first
message when performing the random access procedure, the preamble
including at least one of a size of a third message that the UE will
transmit, and information indicating a channel condition, receiving a
second message from the ENB in response to the first message, the second
message including at least one of uplink (UL) transmission resource
information by which the UE will transmit the third message, and a size
of the third message designated by the ENB, comparing the size of the
third message, designated by the ENB, with a predetermined size, and
designating a format of the third message according to the comparison
result, and generating and transmitting the third message according to
the designated format; wherein based on the format, the third message
includes a normal MAC Packet Data Unit (PDU) or a transparent Radio
Resource Control (RRC) message which is an RRC message that a UE having
no RRC control connection to the ENB transmits for the first time.

[0023] According to further another aspect of the present invention, there
is provided a User Equipment (UE) apparatus for performing a random
access procedure in a mobile communication system. The apparatus includes
a physical layer processor for exchanging messages with an Evolved Node B
(ENB), a Medium Access Control (MAC) controller for controlling to
transmit a preamble to the ENB through a first message, acquiring uplink
(UL) transmission resource information from the ENB in response to the
first message through a second message that the physical layer processor
received from the ENB, the UL transmission resource information being
used for transmitting at least one of a transparent Radio Resource
Control (RRC) message which is an RRC message that a UE having no RRC
control connection transmits for the first time, and Buffer Status Report
(BSR) information indicating an amount of UL data, generating a MAC
control message containing the BSR information, and outputting a format
indicator indicating whether the transparent RRC message or the BSR
information is included in a third message which is transmitted using the
UL transmission resource information and a MAC multiplexer for
multiplexing a MAC control message including at least one of the
transparent RRC message delivered from an upper layer and the BSR
information delivered from the MAC controller, and generating the third
message according to a format indicator designated by MAC controller.

[0024] According to yet another aspect of the present invention, there is
provided a User Equipment (UE) apparatus for performing a random access
procedure in a mobile communication system. The apparatus includes a
physical layer processor for exchanging messages with an Evolved Node B
(ENB), a Medium Access Control (MAC) controller for controlling to
transmit a preamble to the ENB through a first message to perform the
random access procedure, the preamble including at least one of a size of
a third message that the UE will transmit, and information indicating a
channel condition, acquiring at least one of uplink (UL) transmission
resource information by which the UE will transmit the third message, and
a size of the third message, designated by the ENB, in response to the
first message through a second message that the physical layer processor
received from the ENB, comparing the size of the third message,
designated by the ENB, with a predetermined size, and outputting a format
indicator indicating a format of the third message according to the
comparison result, and a MAC multiplexer for multiplexing a MAC control
message including at least one of a transparent Radio Resource Control
(RRC) message delivered from an upper layer and Buffer Status Report
(BSR) information delivered from the MAC controller, generating the third
message according to a format indicator designated by the MAC controller,
and delivering the generated third message to the physical layer
processor; wherein the transparent RRC message is an RRC message that a
UE having no RRC control connection to the ENB transmits for the first
time, and the BSR information indicates an amount of UL data.

[0025] According to still another aspect of the present invention, there
is provided a method for performing a random access procedure by an
Evolved Node B (ENB) in a mobile communication system. The method
includes receiving a preamble for identifying a User Equipment (UE), from
the UE through a first message, transmitting uplink (UL) transmission
resource information through a second message in response to the first
message, the UL transmission resource information being used for
transmitting at least one of a transparent Radio Resource Control (RRC)
message, which is an RRC message that a UE having no control connection
transmits for the first time, and a Buffer Status Report (BSR) indicating
an amount of UL data, receiving a third message transmitted through the
UL transmission resource, checking a format indicator indicating if the
received third message includes the transparent RRC message or the BSR,
and processing the third message in an RRC layer or a Medium Access
Control (MAC) layer according to a set value of the format indicator.

[0026] According to still another aspect of the present invention, there
is provided a method for performing a random access procedure by an
Evolved Node B (ENB) in a mobile communication system. The method
includes receiving a preamble from a User Equipment (UE) through a first
message, the preamble including at least one of a size of a third message
that the UE will transmit, and information indicating a channel
condition; transmitting a second message in response to the first
message, the second message including at least one of uplink (UL)
transmission resource information by which the UE will transmit the third
message, and a size of the third message that the ENB wants to receive,
receiving the third message transmitted through the UL transmission
resource; and processing the third message in a Radio Resource Control
(RRC) layer or a Medium Access Control (MAC) layer according to a format
of the received third message; wherein the format of the third message is
set according to a comparison result between one of the size of the third
message that the UE wants to transmit, or the size of the third message
that the ENB received, and a predetermined size; wherein based on the
format, the third message includes at least one of a normal MAC Packet
Data Unit (PDU) and a transparent RRC message which is an RRC message
that a UE having no RRC control connection to the ENB transmits for the
first time.

[0027] According to still another aspect of the present invention, there
is provided an Evolved Node B (ENB) apparatus for performing a random
access procedure in a mobile communication system. The apparatus includes
a Medium Access Control (MAC) controller for receiving a preamble for
identifying a User Equipment (UE) from the UE through a first message to
perform the random access procedure, transmitting a second message
including uplink (UL) transmission resource information to the UE
corresponding to the preamble, and processing Buffer Status Report (BSR)
information included in a third message received from the UE, a physical
layer processor for exchanging the first message, the second message and
the third message with the UE and a MAC demultiplexer for checking a
format indicator of the third message received from the physical layer
processor to determine if the transparent Radio Resource Control (RRC)
message is included in the third message or the BSR information is
included in the third message, delivering the BSR information to the MAC
controller if the BSR information is included in the third message, and
delivering the transparent RRC message to a Layer 2 (L2) processor if the
transparent RRC message is included in the third message; wherein the
transparent RRC message is an RRC message that a UE having no RRC control
connection to the ENB transmits for the first time, and the BSR
information indicates an amount of UL data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other aspects, features and advantages of the present
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying drawings in
which:

[0029] FIG. 1A is signaling diagram illustrating a process in which a UE
makes a buffer status report by sending a scheduling request message to
an ENB in an LTE system;

[0030] FIG. 1B is a diagram illustrating an example of a BSR message used
in an LTE system;

[0031] FIG. 2 is a diagram illustrating a random access procedure between
a UE and an ENB in an LTE system;

[0032] FIG. 3 is a diagram illustrating a process of making a buffer
status report through a random access procedure according to an
embodiment of the present invention;

[0033] FIG. 4 is a flowchart illustrating an operation in which a UE sends
a status report message according to a first embodiment of the present
invention;

[0034] FIG. 5 is a diagram illustrating a format of a third message (#3),
received through the third message (#3), according to the first
embodiment of the present invention;

[0035] FIG. 6 is a flowchart illustrating an operation in which an ENB
receives a buffer status message from a UE according to the first
embodiment of the present invention;

[0036] FIG. 7 is a diagram illustrating a format of a BSR message
contained in a MAC control message and a format of a BSR message
contained in an RRC message according to a second embodiment of the
present invention;

[0037] FIG. 8 is a flowchart illustrating a method in which a UE sends a
status report message to an ENB according to the second embodiment of the
present invention;

[0038] FIG. 9 is a flowchart illustrating a UE's operation of sending a
BSR message according to the second embodiment of the present invention;

[0039] FIG. 10 is a flowchart illustrating an ENB's operation of receiving
a BSR message from a UE through a random access procedure according to
the second embodiment of the present invention;

[0040] FIG. 11 is a block diagram illustrating structures of a UE and an
ENB for transmitting and receiving a BSR message according to an
embodiment of the present invention;

[0041] FIG. 12 is a diagram illustrating a MAC PDU format defined in the
LTE system to which the present invention is applied;

[0042] FIG. 13 is a diagram illustrating a MAC PDU format according to a
third embodiment of the present invention;

[0043] FIG. 14 is a diagram illustrating an exemplary use of a format
indicator according to the third embodiment of the present invention;

[0044] FIG. 15 is a flowchart illustrating an operation of a UE according
to the third embodiment of the present invention;

[0045] FIG. 16 is a signaling diagram illustrating operations of a UE and
an ENB according to a fourth embodiment of the present invention; and

[0046] FIG. 17 is a flowchart illustrating an operation of a UE according
to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF INVENTION

[0047] Embodiments of the present invention will now be described in
detail with reference to the drawings. For the purposes of clarity and
simplicity, a detailed description of known functions and configurations
incorporated herein has been omitted to provide for a clear and concise
statement of the invention claimed. .

[0048] The present invention provides a method and apparatus by which a
UE, which is allocated no scheduling request resource even though it is
in a connected state, reports its buffer status to an ENB through a
random access procedure.

[0049] With reference to FIG. 2, a brief description will be made of a
random access procedure before a description of embodiments of the
present invention is given.

[0050] FIG. 2 is a diagram illustrating a random access procedure between
a UE and an ENB in an LTE system.

[0051] The random access procedure is a process in which a UE 205, in an
idle mode, transitions to a connected state where its Radio Resource
Control (RRC) connection is set up. The UE 205 establishes UL
synchronization through the random access procedure and sends an RRC
control message. The RRC control message is a message processed in an RRC
layer, and it can be an RRC connection request message in an embodiment
of the present invention. The UE 205 in the idle state selects one code
from a known code set at a predetermined time, and sends it to a
predetermined ENB 210 through predetermined UL transmission resources, as
shown by reference numeral 215. This is expressed as `sending a
preamble`, and it is sent through a first message, referred to as message
#1. As the UE 205 sends a preamble in this way, the ENB 210 can identify
the UE that has sent an allocation request for UL resources to the ENB
210. The UE 205 can then establish UL synchronization with the ENB 210.
Upon receipt of the message #1 including the preamble transmitted by the
UE 205, the ENB 210 sends in step 220 a second message, referred to as
message #2, to the UE 205 in response to the message #1, the message #2
containing UL Timing Adjustment (TA) information and UL grant information
including therein information on the UL transmission resources over which
the UE 205 will send an RRC control message.

[0052] In the communication system based on Orthogonal Frequency Division
Multiplexing (OFDM), as in LTE, the UL signal transmitted by the UE 205
should arrive at the ENB 210 within a predetermined time period. The ENB
210 calculates a UL TA information (indicating a degree by which it can
adjust the scheduled UL transmission time of the UE) for the UE 205 based
on the reception time of the preamble transmitted by the UE 205, and the
TA refers to a UL TA value of the UE 205.

[0053] The UE 205 sends in step 225 a third message, referred to as
message #3, including therein an RRC control message to the ENB 210,
using the transmission resources allocated in step 220 through the UL
grant included in the message #2. Herein, the RRC control message sent in
step 225 through the message #3 can be an RRC connection request message.
Upon receipt of the RRC control message, the ENB 210 performs a
predetermined operation of allowing the UE 205 to transition to the state
where its RRC connection is set up. That is, it performs an operation of
storing UE-related information and setting up a connection between the
upper layer and the UE 205.

[0054] The message #3 that the UE 205 sends to the ENB 210 in step 225, is
generated and processed in a so-called RRC layer, and is classified as an
RRC message. For convenience' sake, the messages exchanged in steps 215
through 225 of the random access procedure are referred to, hereinafter,
as message #1, message #2 and message #3, respectively.

[0055] The ENB 210 sets a size of the message #3 at a small size since it
has no channel state information for the UE 205 that transitions from the
idle mode to the connected state. In the standard conference, 9 bytes are
now considered as the size of the message #3 as shown by reference
numeral 230. In order to provide as much information as possible to the
size-limited message, a transparent mode is applied to the RRC connection
request message 230 which is an RRC control message sent over the message
#3. The term `transparent mode` as used herein refers to a mode of
transmitting only a payload without attaching a header, and it can be
used when a reception side can estimate the information that the header
should provide, depending on its reception situation.

[0056] As described above (FIG. 1B), the MAC header 130 contains
information indicating the destination and size of the data. The
destination of the data indicates in which logical channel or in which
layer device the data was generated, and a reception device delivers the
data to an appropriate layer device depending on the destination
information of the data. If only the RRC connection request message is
exchanged through the message #3, the destination information should not
necessarily be signaled explicitly, and if only one MAC SDU is contained
in the message #3, even the size information of the data should not
necessarily be explicitly signaled.

[0057] For these reasons, at a recent standards conference, a decision was
made to apply the transparent mode to the MAC PDU exchanged through the
message #3. In other words, only the RRC control message is transmitted
in the message #3 without the MAC header as shown by reference numeral
230.

[0058] FIG. 3 is a diagram illustrating a process of making a buffer
status report through a random access procedure according to an
embodiment of the present invention.

[0059] In FIG. 3, in order to send a Buffer Status Report (BSR) message of
a connected-state UE through a random access procedure, a UE 305 selects
an arbitrary code and sends a preamble through a message #1 in step 315,
and sends, in step 325, a message #3 using transmission resources (UL
grant) allocated through the message #2 received from an ENB 310 in step
320. In this case, the message #3 contains a BSR message rather than the
RRC control message. Since the UE 305 attaches no MAC header to the MAC
PDU transmitted through message #3, the ENB 310 cannot determine whether
the MAC PDU received through message #3 is an RRC control message or a
BSR message. In other words, since not only the RRC control message but
also the BSR message are sent through message #3 transmitted in step 325
of the random access procedure, proper information should be provided so
that the reception device can identify the messages.

[0060] A description will now be made of a method and apparatus for
transmitting and receiving a BSR message through a random access
procedure according to first and second embodiments of the present
invention. That is, a description will be made of a method and apparatus
for transmitting and receiving messages between a UE and an ENB during a
random access procedure according to first and second embodiments of the
present invention, and a message generation method therefor.

First Embodiment

[0061] In a first embodiment of the present invention, as a UE, in
transmitting a MAC PDU through a message #3, inserts a MAC header into
the MAC PDU, a device, which has received the MAC PDU, can deliver an RRC
control message or BSR message contained in the MAC PDU to an appropriate
device. The MAC header can be either a normal MAC header, or a MAC header
having a shortened format.

[0062] FIG. 4 is a flowchart illustrating an operation in which a UE sends
a status report message according to a first embodiment of the present
invention.

[0063] In FIG. 4, a message #2 and a message #3 are defined as follows.

[0064] Message #2 is a control message containing TA information and
allocation information of transmission resources through which a UE will
send a UL message in a random access procedure.

[0065] Message #3 is a UL message that a UE sends using the UL
transmission resources allocated through the message #2 in the random
access procedure.

[0066] In step 405, the UE starts a random access procedure if UL data is
generated in the state where the UE is allocated no scheduling request
resource even though there is a need to transition to the connected state
for an arbitrary reason, or it is in the connected state.

[0067] In step 410, the UE selects any one of a plurality of codes through
a predetermined procedure, sends a preamble coded with the selected code,
and then monitors a control channel to receive the message #2 from an
ENB. The number of code is in a preferred aspect equal to 64 codes.

[0068] In step 415, based on the message #2 received from the ENB, the UE
is allocated UL transmission resources, and perceives the UL transmission
resources over which it will send the message #3.

[0069] In step 420, the UE checks a type of the data it will transmit
through the message #3. If the message to transmit through the message #3
is an RRC message, the UE proceeds to step 430, and if the message to
transmit is a BSR message which is a MAC control message, the UE proceeds
to step 425. Although an embodiment of the present invention uses the BSR
message as an example of the MAC control message, it can also use other
messages processed in the MAC layer.

[0070] In step 425, the UE attaches a MAC header to the BSR message. The
MAC header includes therein information indicating that the contained
data is a MAC control message, i.e., a message which is processed in the
MAC layer.

[0071] In the first embodiment of the present invention, since the RRC
message or MAC control message can be sent through the message #3, the
MAC header is needed in order for the reception device to determine
whether the RRC message or MAC control message has been received through
the message #3.

[0072] In step 430, the UE attaches a MAC header to the RRC message. The
MAC header includes information indicating that the contained data is a
message processed in the RRC layer. Thereafter, in step 435, the UE sends
to the ENB the MAC PDU to which the MAC header is attached in step 425 or
430, and performs a predetermined succeeding operation.

[0073] Although the MAC header used for the message #3 may have the same
format as that of the normal MAC header, it may use a separate format
having a size smaller than the normal MAC header for the following
reasons.

[0074] FIG. 5 shows three types of MAC PDU formats used for the message #3
according to the first embodiment of the present invention. In the first
embodiment of the present invention, the UE and ENB use one of the
following three formats.

[0075] The format referred to as reference numeral 500 shows a MAC header
that is comparable in format to a normal MAC header that can be used for
the message #3. In this case, the MAC PDU 500 is composed of a Logical
Channel (LCH) ID 505, a Length Field (LF) 510, and a MAC SDU 515. The LCH
ID 505 is an identifier of a logical channel to which the MAC SDU 515
contained in the MAC PDU 500 belongs. If the MAC SDU 515 is an RRC
message, a logical channel identifier of an RRC processing device is used
as the LCH ID 505. If the MAC SDU 515 is a BSR message, a predetermined
logical channel identifier designated for MAC control information is used
as the LCH ID 505. The LF 510 is information indicating a size of the MAC
SDU 515.

[0076] The format referred to as reference numeral 501 shows that the
optimized MAC header can be used for the message #3. Since only one MAC
SDU is always sent through the message #3, the LF is substantially
unnecessary information. Shown by reference numeral 501 is a MAC PDU
where only an LCH ID 520 is included in the MAC header to reduce
overhead, and the LF is omitted. In this case, only the LCH ID 520 and
MAC SDU 525 are contained in the MAC PDU 501 which is transmitted over
the message #3.

[0077] The LCH ID 520 in the MAC PDU 501 may have a size with which it is
possible to identify the maximum number of logical channels that can be
associated with or set up to one UE. In an aspect of the invention, 5
bits are considered as the size. However, since only two types of data,
i.e., RRC message and MAC control message, are transmitted through the
message #3, 1 bit is enough to identify them. That is, as shown by the
format shown by reference numeral 502, it is also possible to include in
the MAC header only a shorter LCH ID field 525 which is information used
for identifying a logical channel of a MAC SDU 530 with the 1-bit
information. For example, as to the shorter LCH ID field 525, 0 can
indicate that an RRC message is contained, and 1 can indicate that a MAC
control message is contained. If also other types of messages can be
transmitted through the message #3, the shorter LCH ID 525 can be
extended according to the type of transmittable data (2, 3, 4, etc.
bits).

[0078] FIG. 6 is a flowchart illustrating an operation in which an ENB
receives a buffer status message from a UE according to the first
embodiment of the present invention.

[0079] In step 600, the ENB receives a preamble through a message #1 from
a UE that will send a BSR message. In step 605, the ENB sends a message
#2 to the UE corresponding to the preamble. In this case, the message #2
contains therein TA information for the UE and UL transmission resource
information with which the UE will send the BSR message over UL. In step
610, the ENB receives a message #3 from the UE through the UL resources
allocated through the message #2.

[0080] Upon receipt of the message #3, the ENB analyzes multiplexing
information included in the message #3 in step 615 to check whether an
RRC control message is contained in the message #3 or a BSR message which
is a MAC control message is contained in the message #3. As described
above, the normal multiplexing information format can be used intact as
the multiplexing information of the message #3, or the optimized
multiplexing information format can be used as the multiplexing
information of the message #3. The UE and ENB apply a common multiplexing
information format to the message #3.

[0081] If it is determined in step 615 that an RRC message is included in
the message #3, the ENB proceeds to step 625 where it processes the RRC
message by means of an RRC block, and if a BSR message is included in the
message #3, the ENB proceeds to step 620 where it processes the BSR
message by means of a MAC controller.

Second Embodiment

[0082] A second embodiment of the present invention provides a method for
transmitting a BSR message after including it in an RRC message instead
of transmitting only the RRC message through a message #3.

[0083] As a UE, whose RRC connection, a connection having no scheduling
request transmission resource, is set up, includes a BSR message in an
RRC message in transmitting the BSR message through the message #3, only
the RRC message is always contained in the message #3. The use of the
second embodiment of the present invention can avoid overhead due to the
MAC header by applying a transparent mode to the message #3.

[0084] In the second embodiment of the present invention, in transmitting
a BSR message, a UE whose RRC connection is set up, first checks
availability of scheduling request resources, and sends the BSR message
either in the MAC control message or in the RRC message according to the
availability of scheduling request resources. That is, if scheduling
resources are available, the UE sends the BSR message after including it
in the MAC control message, and if scheduling resources are unavailable,
the UE sends the BSR message after including it in the RRC message.

[0085] FIG. 7 is a diagram illustrating a format of a BSR message
contained in a MAC control message and a format of a BSR message
contained in an RRC message according to the second embodiment of the
present invention.

[0086] A MAC control message (MAC control SDU) 720 is composed of a MAC
control message header 710 indicating a type of a control message
contained in the MAC control message, and a BSR message 715 generated in
a predetermined format. The BSR message 715 contains information related
to a buffer status of a UE and other information necessary for
scheduling, for example, transmission power information available for the
UE.

[0087] A header 705 of a MAC PDU 723 containing the MAC control message
contains multiplexing information for the MAC control message 720. The
message format associated with reference numeral 723 does not indicate a
MAC PDU according to the second embodiment of the present invention, but
indicates a MAC PDU format used for sending a normal buffer status
report.

[0088] When the BSR message is sent after it is contained in an RRC
message 725, the MAC control message (MAC control SDU) is mapped to a
predetermined Information Element (IE) of the RRC message 725, which is
called a MAC container 740. The term `IE` as used herein refers to
meaningful information constituting an RRC message, and one RRC message
is composed of multiple IEs.

[0089] When a UE, which is allocated no scheduling request resource even
though its RRC connection is set up, reports a BSR message through a
message #3 transmission, a predetermined RRC message is contained in the
message #3, a MAC control message (MAC control SDU) is contained in an IE
of the MAC container 740 of the predetermined RRC message, and a BSR
message is contained in the MAC control message. The MAC container 740 is
an IE aiming to deliver the information that the MAC layer should
process, to the opposing MAC layer through the RRC message 725.

[0090] Generally, the IE contained in the RRC message 725 is generated in
an RRC block, which is an RRC layer of a transmission side, and analyzed
in an RRC block, which is an RRC layer of a reception side. However, the
information included in the MAC container 740 is generated not in the RRC
block but in a MAC controller, which is a MAC layer of the transmission
side, and analyzed in a MAC controller of a MAC layer of the reception
side, and in the second embodiment of the present invention, the RRC
block only provides a path for transmitting and receiving the MAC
container 740 which includes MAC information. Even in the prior art,
there is an upper layer container, and it sends an upper layer message
after including it in a particular IE of the RRC message 725. However,
since the upper layer message is originally transmitted and received via
the RRC layer, it is natural to transmit/receive the upper layer message
after including it in an upper layer container of an RRC message.

[0091] On the other hand, since a direct path referred to as a MAC control
message 720 exists for transmission/reception of control information
between MAC layers, there is no need, in principle, to define the
so-called MAC container. However, when there is a need to send the MAC
control message through a path prescribed to transmit/receive only the
RRC message 725 like the message #3, it is possible to define the MAC
container 740 and transmit/receive the MAC control message through an RRC
message after including it in the MAC container 740. By
transmitting/receiving the MAC control message through the MAC container
740 in this way, it is possible to avoid adding a separate MAC header to
the message #3. In FIG. 7, an RRC message type 730 represents information
indicating a type of the RRC message 725, and other information 735 means
other IEs contained in the RRC message 725. Since, for each IE,
information indicating a type of the IE is explicitly or implicitly
included in the RRC message 725, an RRC block of the reception device can
identify a MAC container IE in the process of processing IEs of the
received RRC message.

[0092] FIG. 8 is a flowchart/timing chart illustrating a method in which a
UE sends a status report message to an ENB according to the second
embodiment of the present invention.

[0093] In step 815, a Buffer Status Report (BSR) occurs in a UE 805 at an
arbitrary time. The time the BSR occurs in step 815 can include, for
example, the occasion where data abruptly occurs in a buffer of the UE
805. In step 820, the UE 805 determines whether there is any scheduling
request transmission resource (or schedule request resource) allocated to
the UE, and if it is checked that scheduling request transmission
resources are allocated, the UE 805 starts the normal BSR procedure.

[0094] That is, in step 825, the UE 805 sends a scheduling request message
to an ENB 810 through the allocated scheduling request transmission
resources. However, if it is checked in step 820 that there is no
scheduling request resource allocated thereto, the UE 805 proceeds to
step 850 where it sends a status report message through a random access
procedure.

[0095] Returning to step 825, when the ENB 810, which has received the
scheduling request message, allocates in step 830 transmission resources
over which the UE 805 will send a status report message, through UL grant
message, the UE 805 sends in step 835 a MAC control message (MAC control
SDU) containing a BSR message, using the transmission resources allocated
with the UL grant message. The MAC control message is generated according
to a format of the normal MAC PDU as shown by reference numeral 723 (FIG.
7), and is directly exchanged between a MAC controller of a
transmission-side MAC layer and a MAC controller of a reception-side MAC
layer. That is, upon receiving the MAC PDU, a MAC controller 1160 (see
FIG. 11, as will be discussed) in charge of a MAC layer of the ENB 810
directly processes a MAC control message (MAC control SDU) contained in
the MAC PDU.

[0096] In step 840, another BSR occurs in the UE 805 at an arbitrary time.
In step 845, the UE 805 checks if there is any scheduling request
transmission resource allocated thereto. If it is determined in step 845
that the scheduling request transmission resources are released for an
arbitrary reason, so there is no scheduling request transmission resource
available for the UE 805, the UE 805 starts the random access procedure
through steps 850 through 860. However, if it is determined in step 845
that there are scheduling request resources allocated thereto, the UE 805
proceeds to step 825.

[0097] However, since the UE 805, for which it is checked in step 845 for
which there is no scheduling request resource allocated, should send a
BSR message through a random access procedure, the UE 805 selects a
preamble code according to a predetermined procedure and sends a preamble
in step 850, and is allocated UL transmission resources from the ENB 810
through a message #2 in step 855. Thereafter, in step 860, the UE 805
sends a message #3 through the UL transmission resources allocated
through the message #2. In step 860, the UE 805 includes in the message
#3 an RRC message according to the second embodiment of the present
invention.

[0098] The UE 805 includes a MAC container IE containing a BSR message in
an RRC message according to the second embodiment of the present
invention. Upon receiving the message #3 transmitted by the UE 805 in
step 860, a MAC demultiplexer 1150 of the ENB 810 delivers the RRC
message contained in the message #3 to an RRC block 1140 (see FIG. 11)
via a Layer 2 (L2) processor 1145 (FIG. 11). If a MAC container is
included in an IE of the RRC message, it means that a MAC control message
is received through the RRC message, so the RRC block 1140 (FIG. 11)
extracts a MAC control message (MAC control SDU) from the RRC message and
delivers it to the MAC controller 1160 (FIG. 11). Then the MAC controller
1160 (FIG. 11) processes the MAC control message received from the RRC
block 1140. In this case, no MAC header is added to the message #3.

[0099] FIG. 9 is a flowchart illustrating a UE's operation of sending a
BSR message according to the second embodiment of the present invention.

[0100] In this illustrated process, if a BSR message is generated as a BSR
in step 905, the UE checks in step 910 if scheduling request resources
are available. If available, the UE proceeds to step 915, and otherwise,
proceeds to step 935.

[0101] In step 915, the UE starts a normal BSR procedure. That is, in step
915, the UE sends a scheduling request message through the scheduling
request resources. If UL transmission resources are allocated in step
920, the UE generates a BSR message in step 925.

[0102] The BSR message, i.e., MAC control information having a
predetermined format, includes the amount and priority of the data stored
in each buffer of the UE, and also includes transmission power
information available for the UE. In step 930, the UE includes the BSR
message in MAC control information and sends it to an ENB.

[0103] However, a UE, for which it is checked in step 910 that there is no
available scheduling request resource, proceeds to step 935 where it
starts a random access procedure. That is, in step 935, the UE selects a
preamble code by applying a predetermined rule and sends a preamble coded
with the code associated with the ENB. If the UE is allocated, from the
ENB, UL transmission resources for transmission of a message #3 in step
940, the UE generates a BSR message in step 945. In step 950, a MAC
controller 1130 (FIG. 11) of the UE delivers the BSR message or a MAC
control message containing the BSR message to an RRC block 1110 (FIG. 11)
and the RRC block 1110 (FIG. 11) forms a predetermined RRC message to be
transmitted through the message #3, and includes a BSR or a MAC control
message containing the BSR in a MAC container IE of the RRC message.
Thereafter, the UE sends the RRC message containing the MAC container IE
to the ENB.

[0104] FIG. 10 is a flowchart illustrating an ENB's operation of receiving
a BSR message from a UE through a random access procedure according to
the second embodiment of the present invention.

[0105] The ENB receives a preamble from a UE through a message #1 in step
1000, and transmits, through a message #2 in step 1005, UL transmission
resource information to the UE corresponding to the preamble received
through the message #1. In step 1010, the ENB receives a message #3 that
the UE transmitted, through the UL transmission resource information, and
a MAC demultiplexer 1150 (FIG. 11) of the ENB delivers the received
message #3 to an RRC block 1140 (FIG. 11) via an L2 processor 1145 (FIG.
11) since the received message #3 is an RRC control message that should
be processed in an RRC layer. The RRC block 1140 (FIG. 11) of the ENB
checks in step 1015 if MAC control information such as a BSR message is
included in the message #3.

[0106] If it is determined in step 1015 that a MAC control message is
included in the message #3, the RRC block 1140 (FIG. 11) of the ENB
proceeds to step 1025 where it sends the MAC control message to a MAC
controller 1160 (FIG. 11), and the MAC controller 1160 (FIG. 11) performs
an appropriate operation by analyzing the MAC control message.

[0107] However, if it is determined in step 1015 that no MAC control
message is included in the message #3, the RRC block 1140 proceeds to
step 1020 where it analyzes the RRC control information contained in the
RRC control message and performs an operation appropriate thereto.

[0108] FIG. 11 is a block diagram illustrating structures of a UE 1105 and
an ENB 1135 for transmitting and receiving a BSR message according to an
embodiment of the present invention. A transmission device provided in a
UE 1105, includes an RRC block 1110, an L2 processor 1115, a MAC
multiplexer 1120, a MAC controller 1130, and a physical layer processor
1125.

[0109] The RRC block 1110 is a device for processing a control message
related to a radio access network. The RRC block 1110 delivers a BSR
message which is a MAC control message delivered by the MAC controller
1130 to its lower layer after including it in an IE called a MAC
container of an RRC message as shown in FIG. 7, according to the second
embodiment of the present invention. For example, in the first embodiment
of the present invention, the RRC block 1110 generates a MAC SDU included
in a message #3, and in the second embodiment of the present invention,
the RRC block 1110 generates an RRC message including a message #3.

[0110] The L2 processor 1115 takes charge of encrypting the RRC message
generated by the RRC block 1110 and framing it in a size suitable for
transmission over a radio channel. The MAC multiplexer 1120 multiplexes
the MAC SDUs provided from the L2 processor 1115 and the MAC control
message delivered by MAC controller 1130, forms a MAC PDU by attaching a
proper MAC header thereto, and delivers it to the physical layer
processor 1125, which is its lower layer. For example, the MAC
multiplexer 1120 according to the first embodiment of the present
invention multiplexes the MAC SDU containing an RRC message, received
from the L2 processor 1115 which is its upper layer, and the MAC SDU
including a BSR message, received from the MAC controller 1130. For
example, in the second embodiment of the present invention, the MAC
multiplexer 1120 multiplexes the RRC message generated in the RRC block
1110.

[0111] According to the first embodiment of the present invention, the MAC
SDU included in the message #3 is generated in the RRC block 1110, and
the MAC header is generated in the MAC multiplexer 1120. The message #3
in the second embodiment of the present invention is generated in the RRC
block 1110.

[0112] In the first embodiment of the present invention, the MAC
multiplexer 1120 attaches a proper MAC header to the MAC SDU transmitted
through the message #3 during the random access procedure. If the RRC
message is sent through the message #3, i.e., if the MAC SDU is provided
from the L2 processor 1115 connected to the RRC block 1110, the MAC
multiplexer 1120 attaches a proper MAC header indicating that the message
included in the MAC SDU is an RRC message, so that a MAC demultiplexer
1150 in a reception device of an ENB1135 can deliver the MAC SDU to an L2
processor 1145 connected to an RRC block 1140. However, if a MAC control
message is sent over the message #3, the MAC multiplexer 1120 attaches a
proper MAC header indicating that a message included in the MAC control
message is a BSR message, so that the MAC demultiplexer 1150 in the
reception device 1135 can deliver the MAC control message to the MAC
controller 1160.

[0113] If the MAC multiplexer 1120 uses a modified MAC header for the MAC
PDU being sent through the message #3 as shown in FIG. 5, i.e., uses a
MAC header having only a logical channel identifier as shown by reference
numeral 501, or a MAC header having only a shorter logical channel
identifier as shown by reference numeral 502, the MAC multiplexer 1120,
in transmitting an arbitrary MAC PDU, checks if the MAC PDU is sent
through the message #3, and attaches the modified MAC header when it is
sent through the message #3.

[0114] In a third embodiment of the present invention, the MAC multiplexer
1120 multiplexes the MAC SDUs provided from its upper layer, or the MAC
control message generated by the MAC controller 1130, and generates a MAC
PDU by attaching a proper MAC subheader thereto. In particular, in the
case where the first (or initial) RRC message is transmitted through the
message #3 without being contained in the MAC PDU, when the MAC PDU is
sent through message #3, the MAC multiplexer 1120 uses the first bit of
the MAC PDU, i.e., the first bit of the first MAC subheader as a proper
format indicator for indicating whether the first RRC message is
contained in the MAC PDU, and disposes the remaining MAC PDU, except for
the first bit of the first MAC subheader, after the first bit of the MAC
PDU. However, if the first RRC message is contained in the MAC PDU and
then transmitted through the message #3, the MAC multiplexer 1120 uses
the first bit of the MAC PDU as a proper format indicator for indicating
if the first RRC message is contained in the MAC PDU, and disposes the
first RRC message after the first bit.

[0115] In a fourth embodiment of the present invention, the MAC
multiplexer 1120 multiplexes the upper layer data to the MAC PDU using a
MAC PDU format designated by the MAC controller 1130. That is, if the MAC
controller 1130 issues a command to use a format #1, the MAC multiplexer
1120 generates a MAC PDU using a message with a format composed of the
MAC subheaders and the MAC SDU/MAC control information, and if the MAC
controller 1130 issues a command to use a format #2, the MAC multiplexer
1120 generates a MAC PDU using a specific format in which a 1-bit
indicator is included. The format #1 represents a normal MAC PDU format
defined in the LTE system. And the format #2 represents a message format
including therein information used for determining whether only the first
RRC message is contained in the message #3. In addition, in the fourth
embodiment of the present invention, the MAC multiplexer 1120 adds a
header for the message #3 according to a header setting scheme for the
message #3, designated by the MAC controller 1130.

[0116] The MAC controller 1130 is a device for controlling the MAC
multiplexer 1120 and processing the MAC control message. When the random
access procedure is initiated, the MAC controller 1130 controls the
physical layer processor 1125 to determine a code to be used as a
preamble and send a preamble coded with the code. The MAC controller 1130
forms a MAC control message, for example, a BSR message, and delivers it
to the MAC multiplexer 1120. According to an embodiment of the present
invention, the MAC controller 1130 delivers a format indicator indicating
a format of the message #3 to the MAC multiplexer 1120 so that the MAC
multiplexer 1120 can generate a message #3 depending on the format
indicator. In the first embodiment of the present invention, when a BSR
message occurs, the MAC controller 1130 includes it in a MAC SDU and
sends the MAC SDU to the MAC multiplexer 1120, and upon receiving the MAC
SDU from the MAC controller 1130, the MAC multiplexer 1120 attaches
thereto a MAC header indicating that it should be processed in a MAC
layer.

[0117] The MAC controller 1130 according to the second embodiment of the
present invention checks if scheduling request resources are available,
and if scheduling request resources are available, controls the physical
layer processor 1125 to send a scheduling request. If the MAC controller
1130 is allocated UL transmission resources from the ENB, it delivers a
MAC control message containing therein a BSR message to the MAC
multiplexer 1120, and if scheduling request resources are unavailable,
performs the random access procedure, as described above, to control the
physical layer processor 1125 so that it may send a preamble coded with a
selected code, and to deliver a MAC control message containing a BSR
message to the RRC block 1110. Regarding the UL transmission resources,
the physical layer processor 1125 can perceive these resources through
the UL transmission resource information included in the message #2
received from the ENB.

[0118] The MAC controller 1130 according to the third embodiment of the
present invention instructs the MAC multiplexer 1120 to use, or not to
use, a format indicator. That is, for transmission of a message #3 in the
random access procedure, the MAC controller 1130 instructs the MAC
multiplexer 1120 to use the format indicator, or instructs the MAC
multiplexer 1120 not to use the format indicator. In addition, the MAC
controller 1130 acquires UL transmission resource information from the
message #2 received via the physical layer processor 1125, generates a
MAC control message containing the BSR information, and delivers it to
the MAC multiplexer 1120. However, the MAC controller 1130 according to
the fourth embodiment of the present invention compares a size of the
message #3, recognized through the message #2, with a predetermined
reference value X' to determine a format or header setting scheme for the
message #3, and notifies the MAC multiplexer 1120 of the determined
format or header setting scheme.

[0119] The physical layer processor 1125 converts the MAC PDU into a
physical layer signal through a predetermined physical layer procedure
and transmits the physical layer signal. Alternatively, the physical
layer processor 1125 sends a preamble coded with a predetermined code, or
sends a scheduling request message. The MAC controller 1130 according to
the fourth embodiment of the present invention controls to send a
preamble including at least one of the size of the message #3 that the UE
device (transmission device) 1105 will send to perform the random access
procedure, and information indicating the channel condition, to the ENB
through a message #1. In response to the message #1, the MAC controller
1130 acquires at least one of the UL transmission resource information by
which the UE device 1105 will send the message #3, and the size of the
message #3 designated by the ENB, through the message #2 that the
physical layer processor 1125 received from the ENB, compares the size of
the message #3 designated by the ENB with a predetermined size, and
outputs a format indicator indicating a format of the message #3
according to the comparison result. The MAC multiplexer 1120 multiplexes
a MAC control message containing either a transparent RRC message
delivered from its upper layer or BSR information delivered from the MAC
controller 1130, generates the message #3 according to the format
indicator designated by the MAC controller 1130, and delivers it to the
physical layer processor 1125.

[0120] The reception device 1135, provided in the ENB, includes an RRC
block 1140, an L2 processor 1145, a MAC demultiplexer 1150, a MAC
controller 1160, and a physical layer processor 1155.

[0121] The RRC block 1140 is a device for processing a control message
related to a radio access network. According to the second embodiment of
the present invention, if a MAC container IE is contained in an RRC
message received from the L2 processor 1145, the RRC block 1140 delivers
the MAC container IE to the MAC controller 1160.

[0122] The L2 processor 1145performs the operations of decrypting the RRC
message received from the MAC demultiplexer 1150 and restoring a MAC SDU
to its original packet. The MAC demultiplexer 1150 demultiplexes a MAC
SDU and a MAC control message from the MAC PDU delivered by the physical
layer processor 1155, and delivers the MAC SDU, or RRC message, to the L2
processor 1145 for a proper process, and the MAC control message to the
MAC controller 1160. The physical layer processor 1155 exchanges the
messages with the UE. In the first embodiment of the present invention,
the MAC demultiplexer 1150 analyzes a MAC header of the MAC PDU received
through the message #3 during the random access procedure to determine
whether the data contained in the MAC PDU is a MAC SDU containing an RRC
message or a MAC control message containing a BSR message, and delivers
it to a proper device. That is, if the message contained in the MAC PDU
is an RRC message, the MAC demultiplexer 1150 sends the RRC message to
the RRC block 1140 via the L2 processor 1145, and if the contained
message is a MAC control message, the MAC demultiplexer 1150 sends it to
the MAC controller 1160.

[0123] If the MAC demultiplexer 1150 uses a modified MAC header for the
MAC PDU being received through the message #3, i.e., uses a MAC header
having only a logical channel identifier as shown by reference numeral
501, or a MAC header having only a shorter logical channel identifier as
shown by reference numeral 502, the MAC demultiplexer 1150, in processing
an arbitrary MAC PDU, checks if the MAC PDU is received through the
message #3, and if it is received through the message #3, analyzes the
MAC header by applying the modified MAC header format.

[0124] In the third embodiment of the present invention, the MAC
demultiplexer 1150 analyzes the first bit of the message #3 received
during the random access procedure to determine if only the first RRC
message is contained in the message #3, and performs demultiplexing
according thereto. That is, if only the first RRC message is contained in
the message #3, the MAC demultiplexer 1150 delivers the remaining bits
except for the first bit of the first MAC subheader of the message #3 to
the RRC block 1140. If the first bit indicates that not only the first
RRC message is contained in the message #3, the MAC demultiplexer 1150
analyzes MAC subheaders, including the first bit, and demultiplexes the
MAC SDU or MAC control information according thereto, and delivers the
result to a proper upper layer device. The MAC demultiplexer 1150 checks
a format indicator of the message #3 received from the physical layer
processor 1155 to determine whether a transparent RRC message is included
in the message #3 or a BSR information is included in the message #3. If
the BSR information is included in the message #3, the MAC demultiplexer
1150 delivers the BSR information to the MAC controller 1160, and if the
transparent RRC message is included in the message #3, the MAC
demultiplexer 1150 delivers the transparent RRC message to the L2
processor 1145.

[0125] The MAC controller 1160 is a device for processing a MAC control
message. For example, the MAC controller 1160 can make a proper
scheduling decision by analyzing the BSR message contained in the MAC
control message. Although the MAC control message is delivered by the MAC
demultiplexer 1150 in the first embodiment of the present invention, it
can be received from the RRC block 1140 that received the RRC message, in
the second embodiment of the present invention. The MAC controller 1160
receives a preamble for identifying the UE through the message #1 to
perform the random access procedure, sends a message #2 including therein
UL transmission resource information to the UE corresponding to the
preamble, and processes the BSR information included in the message #3
received from the UE.

[0126] With reference to FIGS. 12 through 17, a description is now
provided of a method and apparatus for performing the random access
procedure according to the third and fourth embodiments of the present
invention.

Third Embodiment

[0127] The third embodiment of the present invention provides a method for
indicating if a message #3 contains only a transparent RRC message or
contains a normal MAC PDU, using the first bit or first two bits (two
Most Significant Bit (MSB) bits) of the message #3.

[0128] A transparent RRC message or a normal MAC PDU can be transmitted
through the message #3. The normal MAC PDU is transmitted by a UE that
has no scheduling request resource even though it is in the connected
state, and a BSR message can be include in the MAC PDU. Since data of the
totally different formats having completely different properties is
transmitted through the message #3 , there is a need to include separate
control information in the header so that the reception device can
identify the different formats.

[0129] The above-stated first embodiment of the present invention
represented a shorter LCH ID as a separate control information. However,
the third embodiment of the present invention defines either a 1-bit or
2-bit format indicator as a separate control information other than the
LCH ID described in the first embodiment.

[0130] The term `format indicator` as used herein refers to information
indicating if the first RRC message is contained in a MAC PDU when the
MAC PDU is transmitted through the message #3.

[0131] The format indicator is the first bit (1 MSB bit) or first two bits
(2 MSB bits) of the message #3, and when a transparent RRC message is
transmitted through the message #3, the transmission-scheduled
transparent RRC message is contained (disposed) just after the format
indicator. When a normal MAC PDU containing BSR is transmitted through
the message #3, the first bit (1 MSB bit) or first two bits (2 MSB bits)
of the first MAC subheader among the MAC subheaders constituting one MAC
PDU becomes the format indicator, and the remaining MAC PDU, except for
the first bit or first two bits of the first MAC subheader, is contained
after the format indicator. The bit(s) where the format indicator is
contained is used as a format indicator when a particular condition is
satisfied. When the conditions are not satisfied, the bits are used for
their conventional purpose. The term `particular condition` as used
herein refers to the case where a normal MAC PDU is sent through the
message #3. Therefore, in generating a MAC subheader, the MAC multiplexer
1120 in the transmission device 1105 checks if the MAC PDU is transmitted
through the message #3, and if MAC PDU is transmitted through the message
#3, uses as the format indicator the first bit or first two bits of the
first MAC subheader.

[0132] The MAC controller 1160 in the reception device 1135 also checks
the first bit or first two bits of the data received through the message
#3, and if the first bit or first two bits indicate that a transparent
RRC message is contained in the message #3, the MAC controller 1160
recognizes the remaining part of the message #3 as an RRC message and
delivers it to the RRC block 1140. However, if the first bit or first two
bits of the message #3 indicate that a normal MAC PDU is contained in the
message #3, the MAC controller 1160 in the reception device 1135,
recognizing the whole of the message #3, including the first bit or first
two bits, as a MAC PDU, performs the common MAC PDU process beginning
from the first MAC subheader, including the first bit or first two bits.
The MAC controller 1160 according to the third embodiment of the present
invention receives from the UE a message #1 including a preamble used for
identifying the UE via the physical layer processor 1155 to perform the
random access procedure, sends a message #2 including UL transmission
resource information to the UE corresponding to the preamble via the
physical layer processor 1155, and processes BSR information included in
the message #3 received from the UE. The physical layer processor 1155
according to the third embodiment of the present invention exchanges the
message #1, message #2 and message #3 with the UE device 1105.

[0133] The MAC demultiplexer 1150 in the reception device 1135 checks a
format indicator of the message #3 received from the physical layer
processor 1155 to determine if a transparent RRC message is included in
the message #3 or the BSR information is included in the message #3. If
the BSR information is included in the message #3, the MAC demultiplexer
1150 delivers the BSR information to the MAC controller 1160, and if the
transparent RRC message is included in the message #3, the MAC
demultiplexer 1150 delivers the transparent RRC message to the L2
processor 1145.

[0134] In order to include the format indicator, for which the first bit
(1 MSB bit) or first two bits (2 MSB bits) are used, in the normal MAC
subheader, it is necessary to modify the conventional MAC header
structure. With reference to FIG. 12, a description will now be made of a
structure of a MAC PDU in the system to which the present invention is
applied.

[0135] FIG. 12 is a diagram illustrating a MAC PDU format defined in the
LTE system to which the present invention is applied.

[0136] Referring to FIG. 12, a MAC PDU 1200 is composed of multiple MAC
subheaders 1205 and 1210, and multiple MAC SDU or MAC control information
1215 and 1220. The MAC subheader (e.g., 1205) contains multiplexing
information for the MAC SDU or MAC control information (e.g., 1215). In
other words, as many MAC subheaders as the number of MAC SDU or MAC
control information contained in the MAC PDU are contained in the MAC PDU
1200. The mapping relation between the MAC subheaders and the MAC SDU or
MAC control information is determined according to their contained order.
For example, the first MAC subheader 1205 is associated with the first
MAC SDU or MAC control information 1215, and the second MAC subheader
1210 is associated with the second MAC SDU or MAC control information
1220.

[0137] One MAC subheader contains therein fields of LCID 1225, E 1230 and
LEN 1245, and non-defined R fields 1235 and 1240. LCID 1225, similar to
the above-stated LCH ID, indicates a logical channel identifier of the
MAC SDU and a type of the MAC control information. E 1230 is a field
indicating if the corresponding MAC subheader is the last MAC subheader,
and LEN 1245 is a field indicating a size of the MAC SDU or MAC control
information. In order to reduce a processing load of the
transmission/reception device, the MAC subheaders undergo byte alignment,
and for that purpose, R bits 1235 and 1240, which are the remaining 2
reserved bits, are added.

[0138] The third and fourth embodiments of the present invention use one
or both of the R bits as a Format Indicator (FI), and modifies the
structure of the MAC subheader as shown in FIG. 13 so that the first bit
or first two bits of the MAC PDU can become the format indicator.

[0139] FIG. 13 is a diagram illustrating a MAC PDU format according to the
third embodiment of the present invention.

[0140] The third embodiment of the present invention, unlike in FIG. 12,
moves the R bits in front of the MAC subheader as shown in FIG. 13, and
uses the first R bit 1310 or the two R bits 1310 and 1312 of the first
MAC subheader 1305 as a format indicator. The first R bit 1320 or the
first and second R bits 1320 and 1322 of another MAC subheader other than
the first MAC subheader 1305, for example, of the second MAC subheader
1315, can still be used for their own purposes. Although the R bits are
fields reserved for future use, the first R bit or the first and second R
bits of the remaining MAC subheaders except for the first MAC subheader
1305, if they are given a new purpose in the future, can be used for the
new purpose.

[0141] For example, although the R bits can be defined to contain brief
report information for the buffer status of the UE, the third embodiment
of the present invention allows the first R bit or the first and second R
bits of only the first MAC subheader to contain not the above-stated
information but the format indicator. In order for the R bits to be more
frequently used for their own purpose, it is also possible to apply the
format indicator only to the MAC PDU transmitted over the message #3,
rather than applying the format indicator to all MAC PDUs. That is, while
the first R bit or the first and second R bits of the first MAC subheader
of the MAC PDU being transmitted over the message #3 are used as a format
indicator, the first R bit or the first and second R bits of the first
MAC subheader of another MAC PDU will be used for their original purpose.
For example, for the MAC PDU which is not transmitted through the message
#3, the R bit(s) can be used as reserved bits, or can be used to contain
information indicating the buffer status of the UE.

[0142] FIG. 14 is a diagram illustrating an exemplary use of a format
indicator according to the third embodiment of the present invention.

[0143] In FIG. 14, when a transparent RRC message is transmitted through
the message #3, the message #3 is generated by setting the format
indicator to "0" or to a predetermined value other than "11" as shown by
reference numeral 1405, and disposing a transparent RRC message 1410
after the format indicator. However, when a normal MAC PDU is transmitted
over the message #3, the format indicator is set to "1" or "11" as shown
by reference numeral 1415, and the format indicator is first bit (1 MSB
bit) or first two bits (2 MSB bits) of the first MAC subheader. The
normal MAC PDU can contain therein MAC control information containing BSR
of the UE.

[0144] That is, the `normal MAC PDU` as used herein refers to a MAC PDU in
which MAC control information containing BSR is contained, and in this
case, FI is set to "1" or "11" during its transmission.

[0145] FIG. 15 is a flowchart illustrating an operation of a UE according
to the third embodiment of the present invention.

[0146] If a MAC PDU is generated in step 1505, the UE determines in step
1510 whether it should transmit the MAC PDU through a message #3. That
is, the UE determines if the MAC PDU is generated because of transmission
of the message #3 during a random access procedure. If it is determined
in step 1510 that the UE will transmit the generated MAC PDU through the
message #3, the UE proceeds to step 1520. Otherwise, proceeds to step
1515. In step 1515, the UE generates (builds) a MAC PDU according to the
prior art, and then proceeds to step 1550 where it delivers the MAC PDU
to a lower layer and then ends the process.

[0147] However, if it is detemined in step 1510 that the MAC PDU is
generated because of transmission of the message #3, the UE determines in
step 1520 whether it will transmit a transparent RRC message through the
message #3. The `transparent RRC message` as used herein refers to an RRC
message to which no RLC/MAC header is attached, and it is used herein as
the same meaning as the first RRC message. The `first RRC message` as
used herein refers to an RRC message that the UE having no RRC control
connection transmits for the first time, and since the first RRC message
is transmitted over a common control logical channel called Common
Control Channel (CCCH), it is also expressed as an RRC message being
transmitted over CCCH.

[0148] Therefore, in step 1520, the UE checks if the data to be
transmitted through the message #3 is an RRC message satisfying the
above-stated condition (i.e. an RRC message to which no RLC/MAC header is
attached, an RRC message that the UE having no RRC control connection
transmits for the first time, or an RRC message being transmitted over
CCCH). If the message #3 is an RRC message satisfying the condition, the
UE proceeds to step 1525. Otherwise, proceeds to step 1535. In step 1525,
the UE sets a format indicator to "0" or a predetermined value other than
"11." As described above, the format indicator is a 1-bit or 2-bit
information, and has the following meanings when it is set to "0" (or a
predetermined value other than "11") and "1" (or "11").

[0149] 0 (or a predetermined value other than "11") represents the
condition wherein only the first RRC message is contained in the MAC PDU,
and the first RRC message starts from the next bit of the format
indicator.

[0150] 1 (or "11") represents data other than the first RRC message is
contained in the MAC PDU, and it follows a normal MAC PDU format. A
format indicator is the first bit (1 MSB bit) or first two bits (2 MSB
bits) of the first MAC subheader, and the remaining MAC PDU except for
the first bit or first two bits of the first MAC subheader is contained
from the next bit of the format indicator.

[0151] In step 1530, the UE generates the MAC PDU by attaching the first
RRC message after the format indicator, and then proceeds to step 1550
where it delivers the MAC PDU in which the first RRC message is
contained, to the lower layer, and then ends the process.

[0152] However, in step 1535, the UE determines information that it will
include in the message #3 (or MAC PDU) according to the size of the
message #3. That is, in step 1535, if the UE should include MAC control
information such as BSR in the MAC PDU, it makes MAC control information,
and if the UE should include MAC SDU, or upper layer data, in the MAC
PDU, it receives a MAC SDU delivered from the upper layer.

[0153] In step 1540, the UE generates MAC subheaders for the MAC SDU or
MAC control information that it will include in the MAC PDU. In this
case, the UE uses the first bit or first two bits of the first MAC
subheader as a format indicator, and sets it to a proper value, e.g., 1
or 11, according to the defined meaning of the format indicator.

[0154] In step 1545, the UE generates a MAC PDU by concatenating the MAC
subheaders and the MAC SDU or MAC control information, and then proceeds
to step 1550 where it delivers the MAC PDU to the lower layer and then
ends the process.

Fourth Embodiment

[0155] The fourth embodiment of the present invention provides a method in
which an ENB and a UE implicitly select a format of the message #3
according to a size of the message #3.

[0156] As has been previously described, in the random access procedure,
the UE randomly selects one code from a set of known codes, and sends a
preamble using the selected code. However, 1-bit information indicating
the amount of data that the UE will transmit can be contained in the
preamble together, and the ENB can allocate more transmission resources
to the UE based on the information. That is, the ENB can allocate more
transmission resources for transmission of the message #3 to the UE that
made a report that it has much data to transmit, and can approve a
greater value for the size of the message #3. The 1-bit information being
transmitted in the preamble has the following meanings

[0157] 0 represents a size of the transmission message #3 that exceeds a
predetermined reference value X', and its channel condition is better
than a predetermined reference value Y.

[0158] 1 represents a size of the transmission message #3 that is less
than or equal to a predetermined reference value X', or its channel
condition is worse than a predetermined reference value Y even though the
amount of transmission data is greater than or equal to the predetermined
reference value X'.

[0159] The reference value X' is generally set based on a size of the
first RRC message. Upon receipt of a preamble where the 1 bit is set to
0, the ENB can allocate to the UE transmission resources by which the UE
can transmit data of X' bytes or more. However, upon receipt of a
preamble where the 1 bit is set to 1, the ENB allocates to the UE
transmission resources by which the UE can transmit data of X' bytes or
less.

[0160] However, since the UE transmitting the first RRC message can also
transmit only the first RRC message through the message #3, the UE always
sets, to `1`, the 1-bit information that it transmits through the
preamble, and upon detecting the preamble in which a predetermined bit is
set to `1`, the ENB allocates transmission resources to the UE through a
message #2, by which the UE will transmit data of X' bytes or less. In
other words, since transmission resources, by which the UE will transmit
data of X' bytes or less, are always allocated to the UE transmitting the
first RRC message, allocating transmission resources by which the UE will
transmit data of X' bytes or more means that no first RRC message has
been transmitted through the message #3.

[0161] That is, if the UE has reported to the ENB through the message #1
that the amount of its transmission data exceeds the reference value X'
and its channel condition is better than a predetermined reference value,
and thus the UE will transmit a normal MAC PDU through the message #3, a
format of the message #3 follows the normal MAC PDU format. However, if
the UE has reported through the message #1 that the amount of its
transmission data does not exceed the reference value X' or its channel
condition is worse than the predetermined reference value Y even though
the amount of its transmission data exceeds the reference value X', both
the first RRC message and the normal MAC PDU can be transmitted through
the message #3. Therefore, the fourth embodiment of the present invention
uses, as a format of the message #3, the format by which the reception
device can determine whether only the first RRC message is contained in
the message #3 or the normal MAC PDU is contained in the message #3. For
convenience' sake, the following two formats will be defined as a format
of the message #3.

[0162] Format #1: A normal MAC PDU format defined in the LTE system.

[0163] Format #2: A format including therein information used for
determining whether only the first RRC message is contained in the
message #3 or the normal MAC PDU is contained in the message #3. It can
be either the format proposed in the first or third embodiment of the
present invention, or another format satisfying the above purpose.

[0164] In addition to changing the format of the message #3 according to
the predetermined condition and notifying the changed format, the fourth
embodiment of the present invention can set a message header of the
message #3 according to the predetermined condition and define a header
setting scheme.

[0165] For example, if the UE has reported to the ENB through the message
#1 that the amount of its transmission data exceeds the reference value
X' and its channel condition is better than the predetermined reference
value Y, since it means that the UE will transmit the normal MAC PDU
defined in the LTE system through the message #3, a MAC header setting
scheme for the message #3 follows the normal MAC header setting scheme
defined in the LTE system. However, if the UE has reported to the ENB
through the message #1 that the amount of its transmission data does not
exceed the reference value X' or its channel condition is worse than the
predetermined reference value Y even though the amount of its
transmission data exceeds the reference value X', both the first RRC
message and the normal MAC PDU can be transmitted through the message #3
by the UE.

[0166] Therefore, in setting a header of the message #3 by the UE or a
transmission device, by which the ENB or a reception device can determine
whether only the first RRC message is contained in the message #3 or the
normal MAC PDU is contained in the message #3 according to the fourth
embodiment of the present invention, the setting follows a setting scheme
to which a predetermined limitation is applied. For convenience' sake,
the following two types will be defined as a header setting scheme for
the message #3.

[0167] Header setting scheme #1 represents a scheme for generally setting
a MAC PDU header. There is no limitation in using LCH ID or R bits.

[0168] Header setting scheme #2 represents a header setting scheme which
is applied only when there is a possibility that the first RRC message or
normal MAC PDU will be transmitted through the message #3. There is a
limitation in setting LCH ID or R bits. The header setting scheme #2
limits the use of first several bits of the MAC PDU, thereby making it
possible to determine whether only the first RRC message is contained in
the message #3 or the normal MAC PDU is contained in the message #3. In
the following description, the header setting scheme #2 is assumed to
limit the use of the first 1 bit of the MAC PDU.

[0169] For example, in the third embodiment of the present invention, the
first bit of the MAC PDU is used as an R bit when it follows the header
setting scheme #1 out of the above two header setting schemes, but is
used as a format indicator when it follows the header setting scheme #2.
As another example, when the MAC PDU header is achieved in order of LCH
ID, E, R and R as shown in FIG. 12, it is possible to indicate
inclusion/non-inclusion of the normal MAC PDU or the first RRC message
using the first bit among the 5 bits of LCH ID. In this case, if setting
the first bit to "0" indicates that the first RRC message is contained in
the message #3, the transmission device following the header setting
scheme #2, when the normal MAC PDU is transmitted through the message #3,
should follow the restrictions that the first bit of LCH ID of the first
MAC subheader should be set to `1`, in other words, a MAC SDU having LCH
ID between 16˜31 should be contained in the first MAC SDU of the
MAC PDU.

[0170] Summarizing the fourth embodiment of the present invention, when
the UE has reported through its transmission preamble that the amount of
its transmission data exceeds a predetermined reference value and its
channel condition is better than a predetermined reference value, the UE
and the ENB use the format #1 or the header setting scheme #1 for the
message #3, and otherwise, use the format #2 or the header setting scheme
#2 for the message #3.

[0171] As another method according to the fourth embodiment of the present
invention, when the UE transmits a size of its desired transmission
message #3 through the message #1 and upon receipt of the message #1, the
ENB orders the UE through the message #2 to designate the size of the
message #3 as a predetermined reference value or more, the UE and the ENB
set a header of the message #3 using the format #1 as a format of the
message #3 or using the header setting scheme #1, and otherwise, set a
header of the message #3 using the format #2 as a format of the message
#3 or using the header setting scheme #2.

[0172] Compared with the first method for implicitly determining the
format of the message #3 based on a size of the message #3 that the UE
reported through the preamble, the second method in which the ENB
implicitly determines the format of the message #3 through the contents
of the message #2 including therein the size of the message #3 that the
UE desires to transmit, can be more robust, and the fourth embodiment of
the present invention considers both of the two methods.

[0173] FIG. 16 is a signaling diagram illustrating operations of a UE and
an ENB according to the fourth embodiment of the present invention.

[0174] In step 1615, a UE 1605 starts a random access procedure if a
predetermined condition is satisfied. That is, if a predetermined
condition is satisfied, the UE 1605 selects one code from a set known of
codes, and sends a preamble using the selected code. In this case, the
preamble contains both of a size of the data that the UE 1605 will
transmit through the message #3, and the 1-bit information for the
channel condition.

[0175] Upon receipt of a message #1 including the preamble that the UE
1605 transmitted in step 1615, an ENB 1610 sends in step 1620 a message
#2 containing UL TA information and UL grant information including
therein the size of the message #3 and UL transmission resource
information with which the UE 1605 transmits the message #3, to the UE
1605 in response to the message #1. Upon receipt of the message #2 in
step 1620, the UE perceives the size of the message #3 and transmission
resources over which it will transmit the message #3, and determines in
step 1625 a format of the message #3 or a header setting scheme of the
message #3. As described above, the format of the message #3 or the
header setting scheme of the message #3 is implicitly determined
according to the size of the message #3 or the information that the UE
reported through the message #1. If an agreement is made between the UE
and the ENB to use the format #1 or the header setting scheme #1 when the
size of the message #3 is greater than or equal to a predetermined
reference value, the UE checks the size of the message #3 that the ENB
wants to receive through the message #2, and compares the checked size of
the message #3 with a predetermined reference value. If the size of the
message #3, checked through the message #2, is greater than the reference
value, the UE uses the format #1 as a format of the message #3 or uses
the header setting scheme #1 as a header setting scheme of the message
#3, and otherwise, the UE uses the format #2 as a format of the message
#3 or uses the header setting scheme #2.

[0176] The information reported through the message #1 is the size of the
message #3 that the UE wants to transmit, and the size of the message #3
that the ENB transmitted through the message #2 is the size of the
message #3 that the UE is instructed to transmit by the ENB. However, if
an agreement is made between the UE and the ENB to use the format #1 or
the header setting scheme #1 when the UE has reported to the ENB through
the message #1 that the size of the message #3 that it desires to
transmit is greater than or equal to a predetermined reference value and
its channel condition is better than a predetermined reference value, the
UE determines the format or header setting scheme of the message #3
according to the size of the message #3 and the channel condition
reported through the message #1.

[0177] In step 1630, the UE generates the message #3 using the format
determined in step 1625, or generates the message #3 using the header
setting scheme determined in step 1625, and then sends the generated
message #3 to the ENB. The ENB also determines the format of the message
#3 or the header setting scheme applied to the message #3 by applying the
same rule as that used in the UE, and processes a MAC PDU or first RRC
message contained in the message #3 using the format or header setting
scheme.

[0178] FIG. 17 is a flowchart illustrating an operation of a UE according
to the fourth embodiment of the present invention.

[0179] In step 1705, the UE initiates a random access procedure when a
predetermined condition is satisfied, for example, when the UE
transitions from the idle state to the connected state or transmits UL
data. In step 1710, the UE sends a preamble to an ENB through a
predetermined procedure of selecting one code from a predetermined set of
codes, in order to perform the random access procedure. The preamble can
include therein both the 1-bit information indicating the channel
condition and the size of the message #3 that the UE will transmit.

[0180] After sending the preamble in step 1710, the UE waits to receive
the message #2 that will be transmitted over DL from the ENB through a
predetermined procedure. Upon receiving the message #2 from the ENB in
step 1715, the UE checks UL transmission resource information, contained
the message #2, by which it will transmit the message #3, and size
information of the message #3 that the ENB wants to receive. In step
1720, the UE selects a format of the message #3 or a header setting
scheme that it will apply to the message #3. That is, if it is determined
through the message #2 in step 1720 that the size of the message #3 that
the ENB wants to receive exceeds a predetermined reference value X', the
UE proceeds to step 1725 where it generates the message #3 using the
format #1 or generates the message #3 using the header setting scheme #1.
However, if it is determined in step 1720 that the size of the message
#3, checked through the message #2 received in step 1715, is less than or
equal to the predetermined reference value X', the UE proceeds to step
1730 where it the message #3 using the format #2 or the header setting
scheme #2.

[0181] Alternatively, if the UE has reported through the preamble in step
1710 that the size of the message #3 exceeds the predetermined reference
value X' and its channel condition is better than the predetermined
reference value Y, the UE proceeds to step 1725 where it generates the
message #3 by setting a header of the message #3 using the format #1 or
the header setting scheme #1. Otherwise, the UE proceeds to step 1730
where it generates the message #3 using the format #2. In the present
invention, the X' is determined as a size of the message that the ENB can
receive from the UE located in the cell boundary without difficulty, and
it can be determined through the field test. In step 1725, the UE
generates the message #3 using a normal MAC PDU format, i.e., the normal
MAC PDU format including no 1-bit indicator, described in step 1730, and
then proceeds to step 1735 where it sends the message #3 generated in
step 1725. Alternatively, in step 1725, in setting a header using the
header setting scheme #1, the UE sets a header of the message #3 using
the normal scheme without separate limitation, and then generates and
transmits the message #3 in step 1735.

[0182] In step 1730, the UE generates the message #3 using the format #2,
for example, using the MAC PDU format including a 1-bit indicator, which
is proposed by the fourth embodiment of the present invention, and then
proceeds to step 1735 where it transmits the message #3 generated in step
1730. The 1-bit indicator is a value indicating whether only the first
RRC message is contained in the message #3 (or MAC PDU), and whether the
1-bit indicator indicates that only the first RRC message is contained in
the message #3 or MAC PDU, only the 1-bit indicator and the first RRC
message are contained in the message #3 or MAC PDU, and the RRC message
is contained just after the 1-bit indicator. However, if the 1-bit
indicator indicates that not only the first RRC message is contained in
the message #3 or MAC PDU, the first bit of the message #3 or MAC PDU is
the 1-bit indicator and the normal MAC PDU can be contained in the
remaining part. Also, the first bit of the message #3 can be the 1-bit
indicator as presented in the third embodiment of the present invention.
In this case, it is the first bit of the first MAC subheader, and the
remaining MAC PDU except for the first bit of the first MAC subheader can
be contained in the remaining part.

[0183] Alternatively, in step 1730, the UE generates a header of the
message #3 using the header setting scheme #2, and then proceeds to step
1735 where it transmits the message #3 generated in step 1730.

[0184] As is apparent from the foregoing description, according to the
present invention, in transmitting its BSR message to the ENB, the UE
which is allocated no scheduling request resource can efficiently use the
UL transmission resources by using no L2 header or reducing the size of
the header. Further, according to the present invention, the UE which
performs the random access procedure can efficiently transmit the MAC PDU
or transparent RRC message through the message #3.

[0185] The above-described methods according to the present invention can
be realized in hardware or as software or computer code that can be
stored in a recording medium such as a CD ROM, an RAM, a floppy disk, a
hard disk, or a magneto-optical disk or downloaded over a network, so
that the methods described herein can be executed by such software using
a general purpose computer, or a special processor or in programmable or
dedicated hardware, such as an ASIC or FPGA. As would be understood in
the art, the computer, the processor or the programmable hardware include
memory components, e.g., RAM, ROM, Flash, etc. that may store or receive
software or computer code that when accessed and executed by the
computer, processor or hardware implement the processing methods
described herein.

[0186] While the invention has been shown and described with reference to
a certain preferred embodiment thereof, it will be understood by those
skilled in the art that various changes in form and details may be made
therein without departing from the spirit and scope of the invention as
defined by the appended claims.